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III. Atoms, Elements and Minerals

III. Atoms, Elements and Minerals. A. Changing scales to looking at the elements of the earth and its crust ( 8 most common ) B. Introduction to minerals that comprise rocks ( 11 most common ) C. The silicate minerals ( 7 ) D. Other important rock-forming minerals ( 4 )

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III. Atoms, Elements and Minerals

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  1. III. Atoms, Elements and Minerals A. Changing scales to looking at the elements of the earth and its crust (8 most common) B. Introduction to minerals that comprise rocks (11 most common) C. The silicate minerals (7) D. Other important rock-forming minerals (4) E. Mineral properties

  2. Quartz Biotite Feldspar A. Changing Scale: Zooming in from global view to atomic scale The crust is made of rocks>Rocks are made of minerals > …

  3. A. Changing Scale: Zooming in from global view to atomic scale Rocks are made of minerals > Minerals are made of atoms

  4. Atoms and Elements Electron Shells • Nucleus • Protons • + Charge • Has Mass, Atomic # • Neutrons • 0 Charge • Mass same as One Proton • Atomic Mass # • Electrons • In shells (2, 8, 8…) • - charge (balances each proton +) • Very little Mass

  5. Incomplete electron shells tend to be filled E.g. Chlorine (Cl-) 17 protons (at.# 17) 17 electrons would make it neutral (no charge) with the last shell one electron short {2, 8, 7} Soooo… Tends to grab an electron to fill the third shell Making it a negatively charged Ion (anion) Ions

  6. Ions • Other Common Examples • Sodium, at.# 11 {2, 8, 1}  Na+ • Oxygen, at.# 8 {2,6},  O-2 • Silicon, at.# 14 {2,8,4}  Si+4 Sodium (Cation) Oxygen

  7. Most Common Elements of Earth’s Crust Oxygen: O-2 Silicon: Si+4 Aluminum: Al+3 Iron: Fe+2 or +3 Calcium: Ca+2 Sodium: Na+1 Potassium: K+1 Magnesium: Mg+2

  8. B. Introduction to Minerals • Halite (Rock Salt) • Mineral mined for rock salt and table salt • Na gives electron to Cl • Opposites attract, elements bond • NaCl (Sodium Chloride) *

  9. Repeating 3-D pattern forms a Crystalline Solid (or Crystal) Naturally occurring crystals are Minerals Crystalline structure and bonding leads to physical properties: hardness, crystal form, cleavage specific gravity (density) (pg. 38-43) Intro to Minerals Crystal Form * 3 planes of cleavage

  10. Some Familiar Crystal Forms • Quartz Crystal (SiO2) • Snow Flake (Ice Crystal) due to crystalline structure of H2O Fig. 2.15a

  11. Silica Tetrahedra • The building block of most common rock forming minerals • Four O2-in a tetrahedral configuration • One Si4+ nested in the center • (4  -2) +4= -4 • (SiO4)-4

  12. Silica Tetrahedra • The building block of most common rock forming minerals • Four O2-in a tetrahedral configuration • One Si4+ nested in the center • (4  -2) +4= -4 • (SiO4)-4

  13. Silica Tetrahedra • The building block of most common rock forming minerals • Four O2-in a tetrahedral configuration • One Si4+ nested in the center • (4  -2) +4= -4 • (SiO4)-4

  14. Silica Tetrahedra • The building block of most common rock forming minerals • Four O2-in a tetrahedral configuration • One Si4+ nested in the center • (4  -2) +4= -4 • (SiO4)-4

  15. Silica Tetrahedra • The building block of most common rock forming minerals • Four O2-in a tetrahedral configuration • One Si4+ nested in the center • (4  -2) +4= -4 • (SiO4)-4

  16. Silica Tetrahedra • The building block of most common rock forming minerals • Four O2-in a tetrahedral configuration • One Si4+ nested in the center • (4  -2) +4= -4 • (SiO4)-4

  17. Silica Tetrahedra • The building block of most common rock forming minerals • Four O2-in a tetrahedral configuration • One Si4+ nested in the center • (4  -2) +4= -4 • (SiO4)-4

  18. Silica Tetrahedra • The building block of most common rock forming minerals • Four O2-in a tetrahedral configuration • One Si4+ nested in the center • (4  -2) +4= -4 • (SiO4)-4 -4

  19. Naturally Occurring Crystalline Solid With a definite chemical composition A unique composition or A definite range of compositions Mineral Group, e.g. Olivine Definition of Mineral

  20. Si and O bond in a tetrahedron shape The basic building block of most minerals of the crust Bond with other tetrahedra and cations to form Silicate Minerals C. Silica Tetrahedra and Silicate Minerals * *

  21. Silicate Minerals: Examples • E.g., Olivine • Isolated silicate structure • (SiO4)-4 + 2×Fe+2 • Fe2SiO4 • Fe Mg SiO4 • Mg2SiO4 • (Fe,Mg) 2 SiO4  Olivine Mineral Group Definite Range

  22. Silicate Minerals: Examples • E.g., Olivine • Isolated silicate structure • bonded with iron and magnesium • Makes up much of the mantle • Fe/Mg rich >50% • Silica poor <45% *

  23. Silicate Minerals: Examples • E.g., Pyroxenes (Mineral Group) • Single Chain Silicate structure • (SiO3)-2 + Fe+2 • FeSiO3 • (Fe,Mg) SiO3 • MgSiO3 (Fe,Mg) SiO3  Pyroxene • Mineral Group • Ferromagnesian

  24. Silicate Minerals: Examples • E.g., Pyroxenes (Group of minerals) • Single Chain Silicate structure • bonded with Fe, Mg, Ca, and Al • Found in Oceanic Crust • Fe/Mg/Ca rich (20%) • Silica poor (<20%)

  25. Building Silicates • What is the net charge of: • a silica tetrahedron? • a single chain of single tetrahedra? *Hint: a shared apex is ½ an Oxygen

  26. Building Silicates • What is the net charge of: • a silica tetrahedron? • a single chain of single tetrahedra? • a double chain of tetrahedra? • a sheet of tetrahedra? • a framework of tetrahedra? • a framework of tetrahedra with every fourth silicon replaced with an aluminum ion? • a framework with every other Si replaced with an Al? *Hint: a shared apex is ½ an Oxygen

  27. Building Silicates • What common elements would balance the charges of : • an isolated silicate? • a single chain silicate? • a double chain silicate? • a sheet silicate? • a framework silicate? • a framework of tetrahedra with every fourth silicon replaced with an aluminum ion? • a framework with every other Si replaced with an Al?

  28. Silicate Minerals: Examples • E.g., Pyroxenes (Group of minerals) • Single Chain Silicate structure • bonded with Fe, Mg, Ca, and Al • Found in Oceanic Crust • Fe/Mg/Ca rich • Silica poor *

  29. Single Chain Silicates • E.g., Pyroxenes (SiO3)

  30. Silicate Minerals: Examples • E.g., Amphiboles (Group of minerals) • Double Chain Silicate structure • bonded with Fe, Mg, Ca, and Al • Found in Continental Crust • More silica and less iron than pyroxenes *

  31. Double Chain Silicates • E.g., Amphiboles (Si8O22)

  32. Silicate Minerals: Examples • E.g., Micas(Muscovite and Biotite) • Sheet Silicate structure • bonded with Al, K, (biotite has Fe, Mg) • Found in Continental Crust • More silica and less iron than Amphiboles • E.g., Clays(Mineral Group) • Hydrated, sheet silicates from weathering of other silicates *

  33. Sheet Silicates • E.g., Micas (Biotite and Muscovite)(AlSi3O10)

  34. Silicate Minerals • E.g., Feldspars(Orthoclase and Plagioclase) and Quartz • Framework Silicate • bonded with Al, and K(orthoclase)orNa-Ca(plagioclase) • Found in Continental Crust • More silica than micas, no iron Granite Orthoclase Quartz *

  35. Framework Silicates • E.g., Quartz (SiO2) and Feldspars (AlSi3O8)

  36. Framework Silicates • E.g., Quartz (SiO2) and Feldspar (AlSi3O10)

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